Am in the market, and just saw a "clearance" at Target for similar item @ $~20 for One panel.

However, I want the insulation for HEAT savings, so the "blocking sunlight" feature on the back of these (I'm assuming that mostly means that it's just white) is a bit counter-productive. Wouldn't I want them to have a darker backside rather than a brighter one? I WANT the Sun's heat energy to come in. They need to make them with some sort of zipper/velcro backside so you can swap to a bright back in the Summer and a Dark back in the Winter.

They prevent heat from escaping, so they still provide some heat savings. I'm not 100% sure, but even if the backside was a dark color, if your window is covered by curtains, wouldn't only the back of the curtains get heat from the sun?